Mandelic acid antifoggants



Patented June 12, 1945 2,378,204 I MANDELIC ACID ANrmoocaN'rs George E. Fallesen, Rochester, N. Y., asslgnor to Eastman Kodak Company, Rochester, N. Y., a. corporation of New Jersey No Drawing. Application January 13, 1944, Serial No. 518,124

Claims.

This invention relates to fog inhibitors for photographic emulsions and to photographic emulsions containing them.

It is known that photographic emulsions, particularly ultra-sensitive emulsions, or those containing color sensitizers, exhibit a tendency to form a deposit of silver in the unexposed emulsion. This deposit extends more or less uniformly over the entire emulsion and is known as fog. Photographic fog is of two types, local and general. Local fog is formed by exposure of the film or plate at undesired points, as by a light leak in the camera, or by local action of chemicals. General fog or, as it is sometimes known, chemical fog, is formed in a number of ways. Itmay be caused by the conditions under which the film or plate is stored, such as conditions of high temperature or unusually long time of storage. The nature of the emulsion may also produce chemical fog, as well as the conditions of development of the emulsion, as by development for protracted periods of time or at temperatures above normal. Highly sensitive emulsions are more likely to fog than those of lower sensitivity. I am concerned primarily with general or chemical fog.

It is an object 01 the present invention to provide antifogsing or fog inhibiting agents for ultra-sensitive photographic emulsions and thereby to preserve the emulsion against deterioration resulting in fog. A further object is to provide antii'ogging agents which do not markedly lower the sensitivity of the emulsion. Other objects will appear from the following description of my invention.

These objects are accomplished by developing emulsion, particularly a fast negative emulsion to which may be added optical sensitizing dyes. The emulsion may be one which is intended to be used directly after emulsiflcation or one which is subjected to ripening.

The antifoggantproperties of the dl-mandelic acid salts were tested as follows:

Silver iodobromide was precipitated in 0.8% gelatin solution. After precipitation was complete, the entire volume of emulsion was cooled and divided into portions weighing 1643 grams each. To each portion was added enough gelatin to increase the gelatin concentration to approximately 6.6%. Each portion was then heated to the required digestion temperature, that is, about C. and as soon as this temperature was reached a certain amount of the compound to be tested was added toit. For example, 25 grams of dl-mandelic acid was dissolved in 300 cc. of methyl alcohol, and the sodium salt formed by adding sodium hydroxide solution. The pH of this solution was adjusted to that of the emulsion before adding it to the emulsion. Digestion was then continued for 30 minutes at the specified temperature and the emulsion was then chilled and stored in preparation for shredding and washing. One oi theseportions received no additions other than the required gelatin and it served as the control for all the portions originating from the same precipitation oi. silver halide.

After washing, each emulsion was heated to the optimum point for maximum speed and gamma with acceptable fog. Unsensitized and panchromatized samples of each emulsion so finished were coated by machine on glass plates. After the plates were dry, a series 0! sensitometric tests were made on them. The data were then compared with those oi the check emulsion containing no addendum. These tests include initial tests for speed, gamma and fog, made on the day after coating, similar tests on a second set of plates incubated at F., dryheat, tor- 6 days and a third set of tests made on a third set of plates after having been kept under tropical conditions for 14 days. (The "tropical condi- The amount oi the to; inhibiting aaent used in the emulsion will depend upon the composil to the emulsionsuch as water, methyl alcohol. ethyl alcohol, acetone and others.

3 minutes at so" at. Kodak n-ie developer which had. the following composition:

Monomethyl-p-aminophenol suliate .arams 2.2- Sodium suliite- (desiccated) ;--....-do. 98

The results or tabulated below; 10

- 1 awards ehlorobromidef may be selatin or other suitable colloids such as collo-.

'dion, albumen, cellulose 'orsanic derivatives or synthetic resins.

. p 5 In addition to their use in the sensitive emulmm zgg x- I -17mg?" sion itself, my to: inhibitinz seems may also be Po me 'T', 5 incorporated in the developing solution or in an """i' 1 overcoating or intermediate layer in thephoto- 'zraphic element containin: the sensitive emulsion layer.

'lro eonditionllso. ion-mammoday cubetioaiogtasts tiouioltests WP Emulsion Emulsion Emulsion Emulsion Emulsion with without without with without compound compound compound compound compound compound .os .06 .os i .m .01 .10 .05 .06 .04 .io .08 .10' .015- .os .01 -.l0 .0! .10 I .oo .oo .os- .10 .0? .io

.T eamountoi to: was determined by readins the density at the toe of theeurve after exposure and development of the emulsion, in

tion of the agent and upon the type oi emulsion.

- In general, the amount 0! to: inhibiting agent 3 used will vary from 1 gram told gramsper 1000 cc. of wet emulsion. It will be understood that more or less than this amount may be used. Generally; however, if a greater amount is used 1 in the emulsion, eitherno increased to: inhibit- 3 in: effect is obtained or there-is a decrease in the sensitivity of the emulsion' These com pounds may be incorporated by mixing them with any suitable solvent which is inert with respect The fog inhibiting agents which I have described may-be used in various kinds of photographic emulsions. In addition to being-useful in ordinary non-sensitized emulsions. they may be used in orthochromatic, panchromatic and X-ray emulsions. Various silver salts may be used as the sensitive salt such as silver bromide,

silver chloride, silver bromoiodide, and silver ing a fog-inhibiting amount of an alkali metal jsalt of dl-mandelic acid. I

' 2. A gelatino-silver halide emulsion containinga tog-inhibiting amount or of dl-mandelic acid. i

. 3. A gelatino-silver halide emulsion containing 5 from 1.to l5 grams per liter 01 wet emulsion of sodium salt of dl-mandelic acid. 2 4. The method of reducing the amount of 1 8 produced upon development or a silver halide emulsion, which comprises developing said emulo sion in'the' presence at a fog-inhibiting amount of an alkali metal'salt of dl-mandelic acid.

5. The method of reducing the amount of fog produced upon development of a silver halide emulsion, which comprises developing said emul- 45 sion in the presence of a tog-inhibiting amount of the sodium salt of dl-mandelic acid.

7 GEORGE E. FAILEBEN.

n is to be understood that 1 contemplate as the sodium salt 

